The air battery is a battery including: a solid cathode material (air electrode); an anode material made of metal foil or metal micro-particle; and a liquid or solid electrolyte. The air battery uses: the air or the oxygen gas flowing in the gas passage provided to the inside of the air battery as the cathode active material; and the metal foil or the metal micro-particle as the anode active material.
Many kinds of air battery technologies have been proposed so far. Particularly, research and development of the lithium-air battery are actively conducted recently (see Patent Literatures (PTLs) 1 to 6). Reason for the active research and development of the lithium-air battery is that the energy density per unit weight can be significantly improved compared to the lithium ion battery, which has been put to practical use already, in addition to its usability as a secondary battery capable of being recharged repeatedly.
Among the air battery technologies, the zinc-air battery has been put to practical use (see PTL 7). However, the zinc-air battery is a primary battery incapable of being recharged. Thus, the zinc-air battery is mainly used for the hearing aid since it is light-weighted and low-capacity. In this case, there is no need to make it high-capacity. Therefore, the zinc-air battery is contained in a small-sized metal housing to perform in the practical use.
As an example of air battery, one can mention the fuel cell. In the fuel cell, multiple cells are stacked interspaced by the separator called the bi-polar plate. There are two functions for the bi-polar plate: one is a function to divide two flow passages of the fuel flow for the anode electrode and the air flow for the cathode electrode; and other is a function to directly connect the stacked cells electrically (Non Patent Literature (NPL) 1).
In order to make the stacked battery cell high-capacity, it is necessary for them to be parallel-connected. However, the bi-polar plate is not suitable for that purpose. Moreover, it is very thick and causes a problem of the volume of the battery being too large after stacking the bi-polar plates.
The inventors of the present invention developed a thin cathode structure capable of incorporating the air or oxygen gas, which becomes the cathode active material, into the cathode structure very effectively even if it is stacked with a thin separator and a thin anode structure. Also, they found that a thin lithium-air battery with a large capacity can be produced by using the thin cathode structure with a thin anode structure and a thin separator.
FIG. 1 is an explanatory drawing showing an example of the conventional usage of the thin lithium-air battery. As shown in FIG. 1, the thin lithium battery 101 is used being contained inside of the containment vessel 2201. To the containment vessel 2201, the gas exhaust pipe 2202B and the gas supply pipe 2202A are provided, and parts other than the gas exhaust pipe 2202B and the gas supply pipe 2202A are sealed. The inside of the containment vessel 2201 can be vacuumed by the pump (not shown in FIG. 1) connected to the gas exhaust pipe 2202B. The inside of the containment vessel 2201 can be filled with the air or the oxygen gas by closing the valve 2204 of the gas exhaust pipe 2202B and activating the pump 2203 from the gas supply part (not shown in the drawing) after vacuuming the inside of the containment vessel 2201. When the inside of the containment vessel 2201 is filled with the air or the oxygen gas, the air or the oxygen gas can be supplied to the inside of the thin cathode structure from the opening 99 of the storage case of the thin lithium-air battery 101, allowing the battery reaction to start. Two tabs 97, 98 of the thin lithium-air battery 101 are connected to the blades 2205, 2206 in the containment vessel 2201. The blades 2205, 2206 are connected to the output terminals 2207, 2208. Electricity generated in the thin lithium-air battery 101 can be taken out from the output terminals 2207, 2208.
However, a safely problem still remains. In the conventional containment vessel 2201 shown in FIG. 1, the inside of the vessel is filled with cathode active material and the opening is provided to the thin lithium-air battery 101. Thus, there is non-negligible possibility that the electrolyte or metallic Li, which is the anode material, reacts directly with the oxygen gas or the air.